Welcome to the board.
The replacement parts are a crap shoot at best. I try to purchase parts like that from vendors that actually work on our type of truck. They know what works and what doesn't. The bad thing about LMC is that they don't have a clue what is good and what is bad and they can't answer any technical questions about the parts they sell. There are vendors on here that sell all of the parts you need and you can find them here:
http://67-72chevytrucks.com/vboard/showgroups.php
Just scroll down to the "Gold vendors" and "Platinum Vendors".
When you find a vendor you want to contact click on the name, then click on "Contact Info", then click on the web page link if there is one or you can send them a private message..
There is also a "Vendors Marketplace" here:
http://67-72chevytrucks.com/vboard/showgroups.php
A lot of the board vendors advertise and hang out there...
LockDoc